Electric circuit



' (No Model.)

J. W. MARSH.

ELEGTRIO CIRCUIT.

No. 529,559. Patented Nov. 20,1894.

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UNITED STATES PATENT EEicE.

JOSEPH W'. MARSH, OF PITTSBURG, PENNSYLVANIA.

ELECTRIC CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 529,559, dated November 20, 1894. Application filed April 10, 1894. Serial No. 507,020. (No model.)

To a, whom it may concern:

Be it known that I, JOSEPH W. MARSH, a citizen of the United States, residing at Pittsburg, county of Allegheny, and State of Pennsylvania, have invented certain new and useful Improvements in Electric Circuits, fully described and represented in the following specification andtheaccompanying drawings, forming a part of the same.

This invention relates to electric circuits composed of a pair of conductors formingtwo branches, its object being to provide an improved circuit construction by which the cost of the circuit shall be reduced,and especially to provide a circuit by which the electro static capacity of the conductors and retardation resulting therefrom shall be reduced, while at the same time the circuit is suitable for use out of doors and in other places where there is danger of short circuit ing by moisture.

In conductors of that class in which vibratory or alternating currents are employed, and especially in telephone work, the retardation caused by the electro-static capacity of the conductors is an importantelement, and constant effort has been made, and many arrangements and constructions devised, to reduce this retardation. In making single connections or in running-asingle metallic circuit, it is usual to employ a pair of conductors insulated by fibrous or other material, and twisted together so as to form an anti-induction circuit. If the location be such that there is no danger of short circuiting by moisture, any suitable fibrous or paper insulation may be used, but in making house connections outside or runninga circuit otherwise in moist places, the conductors must be covered with a water proof insulation, and for this some rubber compound is usually employed. Such water proof insulations, however are not only costly but of high specific inductive capacity, which is very objectionable in both telephone and telegraph work, especially the former.

I provide an improved circuit suitable for use where water proof insulation between the conductors is required, which is of much lower electro static capacity than the water proof circuits heretofore in use, by covering one of the pair of conductors with a water proof insulation of any suitable form, and covering the other conductor with insulation of any form suitable for the purpose of insulation, independently of the effect of moisture upon the circuit, some fibrous filled insulation of low specific inductive capacity being preferably used. There is thus secured a water-proof insulation between the two conductors, avoiding short circuiting by moisture, while at the same time but one of the conductors has the water proof cover, and the electro static capacity of the circuit is thus greatly red need, as it is apparent that this capacity will be the mean between the two conductors, one having a low capacity fibrous or other insluation, and the other the high capacity water proof insulation. The construction is also much cheapened, as the water proof insulation is expensive and not durable. By thisconstructionflam enabled to provide an improved electric cable consisting of a bunch of metallic circuits, reducing largely the cost of the construction and the electro static capacity and consequent retardation, over cables in which the conductors are provided with water proof coverings and increasing the efficiency over cables in which the outer covering of the bunch is relied on to exclude moisture, and fibrous orother similar non-water proof insulation used on the separate conductors. Such electric cables are made by bunching together a number of .circuits and covering the bunch with lead or with rubber tape, the latter construction being usually employed for aerial cables. If one of the wires of each circuit be provided with the rubber insulation, and the other with the low capacity fibrous or other insulation, it is obvious that connection between the two conductors of a circuit by moisture is prevented, and leakage of current from the fibrous insulated member of one circuit to the fibrous insulated member of another circuit is of less importance, so that the covering of the bunch may berelied upon to prevent the access of moisture causing such leakage, even though such covering be not absolutely water proof. A construction of small cost and of low electro static capacity, and in which the efficiency will be but slightly reduced by defects in the outer covering may be secured by providing a water proof cover for the bunch and a water proof insulation for one member of each pair.

In the accompanying drawings forming a part of this specification, there is shown for the purpose of illustration an anti-induction electric circuit and cable embodying the invention, Figure 1 being a side view of acircuit and Fig. 2 a cross section of a cable formed of a bunch of such circuits with a water proof covering.

In the drawings, a, b are the two conductors twisted together to form an anti-induction circuit, the conductor a being covered with a water proof insulation 1, and the conductor 1) with a non water proof insulation 2 which may be of any suitable material of low specific inductive capacity.

In Fig. 2 anumberof the circuits are shown as bunched to form a cable and provided with a water proof covering 0.

While the invention is of especial value as applied in circuits and cables where the reduction of the electro static capacity is of importance, and more especially in anti-induction circuits and cables for telephone work, and the invention consists in part of such circuits and cables, it will be understood that the invention includes also circuits for use in electric lighting or elsewhere, where the question of induction or electro static capacity is not of importance, as the invention secures an important improvement in such circuits and cables on account of the reduced cost from using the cheaper and more durable form of insulation for one wire, while at the same. time the electrical connection of the conductors of the circuit by moisture is avoided by the water proof insulation on the other.

What is claimed is 1. An insulated anti-induction electric circuit consisting of a pair of spirally twisted conductors separated by a water proof insulation and by a non water proof insulation of lower specific inductive capacity, said water proof insulation consisting of a covering of one conductor, and said non-water proof insulation consisting of a covering of the other conductor, substantially as described.

2. An insulated electric circuit consisting of a pair of conductors, one conductor hav ing a water proof insulation and the other conductor a non-water proof insulation of lower specific inductive capacity, said separately insulated conductors lying side by side, whereby the conductors are separated by both insulations, substantially as described.

3. An anti-induction electric cable consisting of a bunch of circuits, each circuit consisting of a pair of spirally twisted conductors separated by a water proof insulation and by a non-water proof insulation of lower specific inductive capacity, said water proof insulation consisting of a covering of one conductor, and said non-water proof insulation consisting of a covering of the other conductor, substantially as described.

4.. An anti-induction electric cable consisting of a bunch of circuits and a water proof covering for said bunch, each circuit consisting of a pair of conductors, one conductor having a water proof insulation and the other conductor a non-water proof insulation of lower specific inductive capacity, said separately insulated conductors of each circuit lying side by side, whereby the conductors of each circuit are separated by both insulations, substantially as described.

5. An electric cable consisting of a bunch of circuits and a water proof covering for said bunch, each circuit consisting of a pair of conductors, one conductor having a water proof insulation and the other conductor having a non-water proof insulation, said separately insulated conductors of each circuit lying side by side, whereby the conductors of each circuit are separated by both insulations, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

JOSEPH \V. MARSH.

\Vitnesses:

WM. G. WATT, O. M. HAGEN. 

